The present invention relates to motion compensation devices which compensate for blurring motion of an optical image caused by movement of an optical system. More particularly, the present invention relates to motion compensation devices which control a centering operation of a motion compensation lens during rapid photography.
Image blur suppression devices work within an optical system and have as their object the suppression or reduction of blurring in an image projected onto an image plane. A motion compensation device is a type of image blur suppression device which compensates for motion incident upon the optical system. Motion is typically imparted to the optical system by way of vibrations in the optical system itself, or in a surrounding holding member. In general, known motion compensation devices cause a compensation lens to shift counter to the motion of the optical system so as to shift the image projected by the optical system relative to the optical system.
Conventional motion compensation devices detect motion of an optical system, such as a camera, by way of a sensor and move a motion compensation lens perpendicular to an optical axis in accordance with a detected output of the sensor. The motion compensation device then compensates to fix a subject image on an image plane.
FIG. 8 (PRIOR ART) illustrates operation of a conventional motion compensation device. As illustrated in FIG. 8 (PRIOR ART), a photographic image plane 52 moves in response to driving of a motion compensation lens with a conventional motion compensation device. A photographer using a conventional motion compensation device half depresses a shutter button to photograph a subject 51 in photographic image plane 52 and to commence motion compensation by the motion compensation device. If no motion compensation is performed, a blurring motion is present in photographic image plane 52. However, when the motion compensation operation is repeatedly performed for a predetermined period of time, photographic image plane 52 shifts to become photographic image plane 53. When the photographer releases the shutter button, the motion compensation device stops.
Upon completion of the motion compensation, the motion compensation lens is moved to a center of an optical axis through a centering operation to prepare for a next photographic operation. During execution of a next motion compensation operation, the motion compensation lens moves from the center of the optical axis.
The conventional motion compensation device performs the motion compensation operation in response to half depression of the shutter button and sets a center of the motion compensation lens in a position separate from center of the optical axis. When photography is subsequently performed, the center of the motion compensation lens resumes movement from this position, reaches a boundary of a motion compensation range, and is unable to further perform motion compensation.
After the photographer has half depressed the shutter button, and the shutter button is fully depressed, motion compensation is resumed. Once the motion compensation operation is stopped, and after the centering operation has been performed, motion compensation operation may again resume. Then, after an exposure has been performed by opening and closing a shutter, motion compensation operation ends, and a subsequent centering operation is performed such that the camera is ready for a next photographic operation.
As illustrated in FIG. 8A (PRIOR ART), when the conventional motion compensation device commences motion compensation from a rest position, i.e. from a position where motion compensation is not performed, photographic image plane 52 moves to become photographic image plane 53. Thus, when the blurring motion compensation device performs a centering operation, the printed photographic image plane 52 is unexpectedly changed to photographic image plane 54.
In view of the above, when a photographer looks through a viewfinder of an optical system, such as a viewfinder of a single lens reflex camera, upon release of a half depressed shutter button, photographic image plane 52 becomes stationary due to motion compensation, but unexpectedly moves to become photographic image plane 54. In this manner, when motion compensation is performed, there is a problem that a photographic image is poorly set because the photographic image plane unexpectedly changes to a different photographic image plane.
Moreover, through full depression of the shutter button from the half depressed state, when exposure is performed after the centering operation has been performed, there is a problem that a photograph is taken of an unintended location.
In a camera equipped with a film autowind device, a conventional motion compensation device stops motion compensation for each frame of photography and also performs a centering operation between frames. During operation, a photographic frame which is subsequent to photographic image plane 52 subsequently becomes image plane 54. Furthermore, because photographs are taken in rapid succession, a problem is encountered that photographs taken with motion compensation are not intended by a photographer.